Sodium Metabisulfite

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Sodium Sulfite, Potassium Sulfite, Ammonium Sulfite, Sodium Bisulfite, Ammonium Bisulfite, Sodium Metabisulfite and Potassium Metabisulfite are inorganic sulfite salts. In cosmetics and personal care products, these ingredients are used in the formulation of permanent waves, hair bleaches, hair dyes, colors and tints, and in some bath and skin care products.

Why is it used in cosmetics and personal care products?

All these ingredients function as reducing agents, which means they donate hydrogen molecules to other substances in cosmetics and personal care products. With the exception of Sodium Metabisulfite, these ingredients also modify hair fibers to facilitate changes to the structure of the fibers, such as with permanent waves or with hair straightening. In addition, Sodium Sulfite, Potassium Sulfite, Sodium Bisulfite and Sodium Metabisulfite function as antioxidants preventing or slowing deterioration of cosmetics and personal care products caused by chemical reactions with oxygen.

The Food and Drug Administration (FDA) includes Sodium Sulfite, Sodium Bisulfite, Potassium Bisulfite, Sodium Metabisulfite and Potassium Metabisulfite on its list of substances considered Generally Recognized As Safe (GRAS) for use as chemical preservatives in food. They are not to be used in meats, in foods recognized as sources of vitamin B1, or on raw fruits and vegetables. Because some people are sensitive to sulfites, food containing these ingredients must be clearly labeled.

The safety of Sodium Sulfite, Potassium Sulfite, Ammonium Sulfite, Sodium Bisulfite, Ammonium Bisulfite, Sodium Metabisulfite and Potassium Metabisulfite has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. The CIR Expert Panel evaluated the scientific data and concluded that all seven ingredients were safe as used in cosmetics and personal care products.

More safety Information:

CIR Safety Review: Sodium Sulfite, Sodium Metabisulfite and Potassium Metabisulfite were negative in mutagenicity studies. Some positive results were noted for Sodium Bisulfite in in vitro, but not in in vivo studies. In was noted that in in vitro assays, an equilbrium would exist between sulfurous acid, sulfur dioxide, bisulfite, sulfite and metabisulfite.

The CIR Expert Panel concluded that the positive results in the in vitro assays were a result of the presence of the bisulfite form. In cosmetic and personal care products, even with the addition of bisulfite, the sulfite form would predominate.

In mammals, the presence of the enzyme, sufate oxidase, would convert all sulfite to sulfate. In addition, the highly charged nature of these ingredients would result in relatively low dermal penetration.

Sodium Sulfite, Potassium Sulfite, and Ammonium Sulfite are listed as inorganic sulphites and hydrogen sulphites in Annex VI, Part I (preservatives which cosmetic products may contain) of the Cosmetics Regulation of the European Union and may be used at a maximum authorized concentration of 0.2%, expressed as free sulfur dioxide.

The Joint FAO/WHO Expert Committee on Food Additives has established a group Acceptable Daily Intake of 0.7 mg/kg body weight for sulfur dioxide and sulfites expressed as sulfur dioxide, which includes Sodium Sulfite, Sodium Metabisulfite and Potassium Metabisulfite.